Marble Casing?

I'm currently building a 300W Tripath-based power amp from 41hz.com and am thinkinking of placing it inside a custom-built marble case. This will effectively be a 3 sided box with cut-outs for the switches on the front. The heatsink from the amp will form about 2/3 of the rear plate, along with a piece of aluminium with the binding posts and grommets for the PSU input. Is there any reason why I shouldn't use marble and should stick to a metal case? The reason I want to use the marble is that I know someone who can get it made fairly cheaply and I think it will look the B's & E's.

 

The only possible reasons I can think of are:
- Heat dissipation. Normal metal cases are usually very useful for this. Marble is likely to be rubbish. Having said that, you're talking about a Tripath solution, which might not produce as much heat. A thought is to suggest that you build the circuit first and see how hot the unit runs without a case. If it's cool, then go with marble.
- I guess that marble will be difficult to cut holes in for the controls and might be easy to chip. Not that I've got any experience of it.

 

Only thing to add to the comments above is I suppose that the marble won't be able to act as a screen (unless lined with metal) and possibly given the high frequencies they run at the Tripath chips may be susceptible to RFI?

Keep us posted with how you get on with the amp I'll be very interested to hear your views when it's done.

 

HTML:

Only thing to add to the comments above is I suppose that the marble won't be able to act as a screen (unless lined with metal) and possibly given the high frequencies they run at the Tripath chips may be susceptible to RFI?

HTML:

If I want to line the unit what's the recommended material for doing this?

 

My comment was very naive I'm afraid, this isn't something I know about. I have a feeling some people use copper foil though? That said, you do get pieces of kit with plastic cases, so I'd ask someone who knows about the Tripath chips. Tone would know of course.

 

look to do the front of the case...marble is expensive and difficult to work. As people have said it offers limited rfi rejection [which may or may not be an issue]

 

maplin do alu sheets pretty cheap. I've used those to line wooden chassis before. Can't remember if its 1 or 2mm (1 I think) but very easy to work and using a few pieces to build up the thickness makes it less suseptable to emi from transformers if thats an issue (worked well in my phono).

 

You can buy conductive paint for RFI shielding of non shelding substrates/cabinets, plastic, ceramic etc. Farnell sell it as do Maplin and RS.

 

RFI shielding

I would be tempted to use thin copper sheet from RS. It's easy to cut with tin snips can be folded and soldered to form a complete shield. Aluminium is by contrast hard to form as it can't be joined unless you have a TIG welder.

 

I use off the shelf angle iron and some nuts and bolts. If the case is square and you have a jig saw its fine, takes no longer than bending stuff to fit.